It is expected that a 3D broadcast service, which displays three-dimensional (3D) images on a screen and allows viewers to enjoy stereoscopic video, will be widely available from now on. Transmission methods for 3D video are defined in HDMI Ver. 1.4. In addition to a frame packing system, systems such as side by side (which is also referred to as Side By Side; SBS, or a side-by-side system) and the like are also defined as informative (reference information) systems. As transmission systems for 3D images, in addition to the side-by-side system, there are an over/under (which is also referred to as Over-Under, a vertical division system, Top/Bottom, Above/Below, or the like) system, a frame sequential (Frame Sequential; FSQ) system, and the like.
The frame packing system is a system that transmits left eye video and right eye video in pairs. The side-by-side system is a system that transmits video in a state in which the screen is divided into left and right halves. With a video display device that is compatible with the side-by-side system, it is possible to create stereoscopic video from divided left and right images. However, with a non-compatible video display device, a right eye image is displayed on the right side of the screen and a left eye image is displayed on the left side of the screen, respectively. The over/under system is a system that transmits video in a state in which the screen is divided into upper and lower halves. Similarly to the side-by-side system, with a video display device that is compatible with the over/under system, it is possible to create stereoscopic video from divided upper and lower images. However, with a non-compatible video display device, same images are displayed vertically symmetrically. The frame sequential system is a system that sequentially switches and outputs a right eye video stream and a left eye video stream in a time sharing manner.
When video transmitted by this type of 3D video transmission system is displayed, for example, by a time sharing stereoscopic video display system (refer to Patent Literatures 1 to 3, for example) that uses so-called shutter glasses, it is possible to cause the viewers to perceive the video as stereoscopic video. The frame packing system and the frame sequential system transmit two video images for the left eye and the right eye, and therefore, they are transmitted at a transfer rate that is twice that of 2D video transmission with the same resolution. With the side-by-side system and with the over/under system, left-eye 3D video and right-eye 3D video each have a half resolution, vertically or horizontally. Therefore, the 3D video as a whole is transmitted at the same transfer rate as that of the 2D video.
In determining a video format of the video transmitted by HDMI, the video format of 2D video can be determined from information, such as a pixel frequency of a video signal, timing information such as Hactive, Hblank, Vactive, Vblank and Vfreq, and VIC (Video Format Identification Code, resolution/frame rate information) in an AVI InfoFrame. However, in a case of 3D video, in addition to the above-described information, information such as an “InfoFrame that transmits 3D information” (which includes information indicating that 3D video is being transmitted, and information indicating a type of the 3D system of the video, such as Frame Packing, Side-by-Side (Half) or the like, refer for details to the HDMI standard Ver. 1.4, Chapter 8.2.3, Appendix H) as defined in the HDMI standard Ver. 1.4 is also necessary to identify the video format.
When the output resolution is changed between 2D video and 3D video, if switching is performed between 2D video and 3D video with the frame packing system, the video transfer rate also changes. Therefore, in a similar manner to a resolution change in 2D video (for example, switching between 720 p and 1080 p), it is necessary to temporarily stop the video signal output at the time of switching. When HDCP (a High-bandwidth Digital Content Protection system) is used for encryption and output is performed, HDCP authentication is necessary at the time of switching and a black screen appears for about one or two seconds.
On the other hand, when switching is performed between 2D video and 3D video with the side-by-side system, if the same image size and the same frame rate are used, video transfer rates are also the same. Therefore, without stopping the output of the video signal, the switching can be performed just by starting/stopping the output of the InfoFrame that transmits 3D information.